Module 6 : Traffic Intersection Control

Lecture 33 : Grade Separated Intersection

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	Diamond Interchange The diamond Interchange is the simplest form of grade separated intersection between two roadways. The conflicts between through and crossing traffic are eliminated by a bridge structure. This particular intersection has four one way ramps which are essentially parallel to the major artery. The left turn crossing movement conflicts are considerably reduced by eliminating the conflict with the traffic in opposite direction. All the remaining left turn conflicts, merging and diverging maneuver conflicts take place at the terminal point of each ramp. Limitation in application of this design depends on the operations of these terminals. So, it is suitable for locations where the volume of left turn traffic is relatively low. The diamond interchange requires a minimum amount of land and is economical to construct. Also,a diamond interchange generally requires less out-of-the-way travel and vehicle operating costs are less than those on most other types of interchanges. The single point of exit from the major roadway eases the problem of signing. This type of interchange requires the least of right-of-way. With these advantages, the diamonds appear to be the ideal solution to an intersection problem. But there might be chances of occurrence of conflicts at the locations where ramps meet the grade separated cross street are to be considered foe high ramp volumes. Improper design of signal timings at cross streets may result in the inadequacy of capacity for certain flows.